U.S. patent application number 12/851842 was filed with the patent office on 2011-02-10 for two-part organopolysiloxane composition.
This patent application is currently assigned to Shin-Etsu Chemical Co., Ltd.. Invention is credited to Tadashi ARAKI, Tsuneo KIMURA.
Application Number | 20110034613 12/851842 |
Document ID | / |
Family ID | 43535311 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110034613 |
Kind Code |
A1 |
ARAKI; Tadashi ; et
al. |
February 10, 2011 |
TWO-PART ORGANOPOLYSILOXANE COMPOSITION
Abstract
A two-part organopolysiloxane composition is provided. A first
part comprises (A) an organopolysiloxane, (B) a ketene silyl acetal
compound or 2-methyldialkoxysilylpropionic ester, (C) an organic
compound or silane compound having at least one nitrogen atom, (D)
a silane compound having at least two alkoxy groups, and (E)
another ketene silyl acetal compound or 2-trialkoxysilylpropionic
ester. A second part comprises (F) an organopolysiloxane, (G) an
organotin catalyst, and (H) water. The first and second parts are
mixed to form a sealing composition which is fast curable to the
depth with alcohol removal.
Inventors: |
ARAKI; Tadashi; (Annaka-shi,
JP) ; KIMURA; Tsuneo; (Annaka-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Shin-Etsu Chemical Co.,
Ltd.
Chiyoda-ku
JP
|
Family ID: |
43535311 |
Appl. No.: |
12/851842 |
Filed: |
August 6, 2010 |
Current U.S.
Class: |
524/500 |
Current CPC
Class: |
C08K 5/5419 20130101;
C09J 183/04 20130101; C09J 183/04 20130101; C08K 5/57 20130101;
C08L 83/00 20130101; C08L 83/04 20130101; C08L 83/00 20130101; C08L
83/00 20130101; C08G 77/16 20130101; C08L 83/04 20130101; C08K
5/5425 20130101 |
Class at
Publication: |
524/500 |
International
Class: |
C08L 83/06 20060101
C08L083/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2009 |
JP |
2009-185585 |
Claims
1. A two-part organopolysiloxane composition comprising first and
second parts wherein the composition cures after the first and
second parts are mixed together, said first part comprising (A) 50
to 190 parts by weight of an organopolysiloxane having the general
formula (1): HO(SiR.sup.1.sub.2O).sub.nH (1) wherein R.sup.1 is
each independently a substituted or unsubstituted monovalent
hydrocarbon group of 1 to 10 carbon atoms, and n is an integer of
at least 10, (B) 0.1 to 20 parts by weight of at least one compound
selected from the group consisting of a ketene silyl acetal
compound having the general formula (2), a
2-methyldialkoxysilylpropionic ester having the general formula
(3), and partial hydrolyzates thereof,
(R.sup.2O).sub.2Si(R.sup.3)OC(OR.sup.3)CHCH.sub.3 (2)
(R.sup.2O).sub.2Si(CH.sub.3)CH(CH.sub.3)COOR.sup.3 (3) wherein
R.sup.2 is an alkyl group of 1 to 4 carbon atoms, R.sup.3 is a
substituted or unsubstituted alkyl group of 1 to 12 carbon atoms,
R.sup.2 and R.sup.3 may be the same or different, (C) 0.01 to 20
parts by weight of an organic compound having at least one nitrogen
atom in the molecule and/or a silane compound having at least one
nitrogen atom in the molecule, (D) 0.1 to 30 parts by weight of a
silane compound having at least two alkoxy groups in the molecule,
represented by the general formula (4), or a partial hydrolytic
condensate thereof, R.sup.5.sub.mSi(OR.sup.4).sub.4-m (4) wherein
R.sup.4 is an unsubstituted or alkoxy-substituted monovalent
hydrocarbon group of 1 to 4 carbon atoms, R.sup.5 is a substituted
or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon
atoms, and m is 0, 1 or 2, and (E) 0.1 to 10 parts by weight of at
least one compound selected from the group consisting of a ketene
silyl acetal compound having the general formula (5), a
2-trialkoxysilylpropionic ester having the general formula (6), and
partial hydrolyzates thereof,
(R.sup.2O).sub.3SiOC(OR.sup.3)CHCH.sub.3 (5)
(R.sup.2O).sub.3SiCH(CH.sub.3)COOR.sup.3 (6) wherein R.sup.2 and
R.sup.3 are as defined above, said second part comprising (F) 150
to 10 parts by weight of an organopolysiloxane having the general
formula (7): HO(SiR.sup.1.sub.2O).sub.nH (7) wherein R.sup.1 and n
are as defined above, (G) 0.01 to 10 parts by weight of an
organotin catalyst, and (H) 0.1 to 10 parts by weight of water,
with the proviso that the total amount of components (A) and (F) is
200 parts by weight, and the amounts of components (B) to (E) in
the first part and the amounts of components (G) and (H) in the
second part are relative to the total amount of components (A) and
(F) which is 200 parts by weight.
2. The composition of claim 1 wherein component (A) is 80 to 120
parts by weight and component (F) is 120 to 80 parts by weight,
with the proviso that the total amount of components (A) and (F) is
200 parts by weight.
3. The composition of claim 1 which is used as a sealant in
automotive parts or electrical and electronic parts.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn.119(a) on Patent Application No. 2009-185585 filed in
Japan on Aug. 10, 2009, the entire contents of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to a two-part organopolysiloxane
composition of the dealcoholization type which is fast curable to
depth.
BACKGROUND ART
[0003] Room temperature fast-curable organopolysiloxane
compositions of the condensation cure type which are known in the
art include one-part compositions comprising a hydroxy-terminated
organopolysiloxane as a base polymer and a crosslinker wherein the
amount of the crosslinker is minimized to improve a crosslinking
rate through hydrolysis, and two-part compositions wherein a
hydroxy-terminated organopolysiloxane as a base polymer and a
crosslinker are separately packed and mixed on use.
[0004] One-part compositions are not regarded fast-curable despite
a high cure rate from the surface, because deep-section cure takes
a certain time. It is believed that two-part compositions are
effective where fast cure is of high priority. Although two-part
compositions of the condensation cure type are relatively good in
deep-section cure, they are cumbersome to handle and unamenable to
automatic mixers or dispensers because two parts are mixed in a
different volume ratio from 1:1. For complete cure to the depth, it
is necessary to strictly determine the amount of crosslinker added
relative to the amount of terminal hydroxy groups of
organopolysiloxane or to add water as a deep-section curing
agent.
[0005] On the other hand, organopolysiloxane compositions of the
addition cure type are advantageous in working because two parts
are mixed in a ratio of 1:1. However, heating ovens are usually
necessary for curing. Also the working environment is limited since
the curing catalyst can be poisoned in the presence of an addition
poison.
[0006] JP 3916403 discloses a composition comprising a
diorganopolysiloxane blocked at both ends of the molecular chain
with hydrolyzable hydroxy groups, an organic compound having at
least one carbonyl group (C.dbd.O) in the molecule, and an organic
compound having at least one primary amino group (NH.sub.2) in the
molecule. This composition is intended to improve deep-section cure
and fast-cure by utilizing water produced additionally from
ketimine-forming reaction between carbonyl and primary amino
groups. Thus the composition is improved in deep-section cure and
fast-cure. However, when heat is applied in the uncured state, the
dialkylketoxime which is the condensation reaction product is
quickly gasified whereby bubbles are introduced in the cured
composition, bringing a substantial drop in sealing capability,
which is undesirable particularly in the automotive oil-seal
application. JP 3970484 overcomes the problem by limiting the type
and amount of the curing agent so as to prevent bubble formation in
the cured composition.
[0007] Although these patents propose an effective approach, a
problem arises when this approach is applied to organopolysiloxane
compositions of the dealcoholization type. The cure rate is
slightly accelerated, but apparently slow as compared with the
compositions of the deoximation type. Thus the approach is not
applicable in the automobile and electrical and electronic
industries where fast cure is required. Even when the conventional
measure of adding water as the deep-section curing agent is
employed for the purpose of improving cure, no dramatic improvement
in cure is achieved.
[0008] Citation List
[0009] Patent Document 1: JP 3916403
[0010] Patent Document 2: JP 3970484
SUMMARY OF INVENTION
[0011] An object of the invention is to provide a two-part
organopolysiloxane composition of the dealcoholization type which
is fast curable to depth.
[0012] The inventors have found that cure takes place immediately
after a ketene silyl acetal compound of formula (5), shown below,
2-methyldialkoxysilylpropionic ester of formula (6), shown below,
or partial hydrolyzate thereof is mixed with silanol groups in air
in the presence of an organic compound having at least one nitrogen
atom. By placing the ketene silyl acetal compound of formula (5),
2-methyldialkoxysilylpropionic ester of formula (6) or partial
hydrolyzate thereof in a first part substantially free of silanol
groups, and mixing the first part with a silanol group-containing
second part, there is obtained a mixture which is drastically
improved in cure behavior. When water is placed in the second part,
a better fast-cure behavior is obtained. The invention is
predicated on these findings.
[0013] The invention provides a two-part organopolysiloxane
composition comprising first and second parts wherein the
composition cures after the first and second parts are mixed
together. The first part comprises:
[0014] (A) 50 to 190 parts by weight of an organopolysiloxane
having the general formula (1):
HO(SiR.sup.1.sub.2O).sub.nH (1)
wherein R.sup.1 is each independently a substituted or
unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms,
and n is an integer of at least 10,
[0015] (B) 0.1 to 20 parts by weight of at least one compound
selected from the group consisting of a ketene silyl acetal
compound having the general formula (2), a
2-methyldialkoxysilylpropionic ester having the general formula
(3), and partial hydrolyzates thereof,
(R.sup.2O).sub.2Si(R.sup.3)OC(OR.sup.3)CHCH.sub.3 (2)
(R.sup.2O).sub.2Si(CH.sub.3)CH(CH.sub.3)COOR.sup.3 (3)
wherein R.sup.2 is an alkyl group of 1 to 4 carbon atoms, R.sup.3
is a substituted or unsubstituted alkyl group of 1 to 12 carbon
atoms, R.sup.2 and R.sup.3 may be the same or different,
[0016] (C) 0.01 to 20 parts by weight of an organic compound having
at least one nitrogen atom in the molecule and/or a silane compound
having at least one nitrogen atom in the molecule,
[0017] (D) 0.1 to 30 parts by weight of a silane compound having at
least two alkoxy groups in the molecule, represented by the general
formula (4), or a partial hydrolytic condensate thereof,
R.sup.5.sub.mSi(OR.sup.4).sub.4-m (4)
wherein R.sup.4 is an unsubstituted or alkoxy-substituted
monovalent hydrocarbon group of 1 to 4 carbon atoms, R.sup.5 is a
substituted or unsubstituted monovalent hydrocarbon group of 1 to
10 carbon atoms, and m is 0, 1 or 2, and
[0018] (E) 0.1 to 10 parts by weight of at least one compound
selected from the group consisting of a ketene silyl acetal
compound having the general formula (5), a
2-trialkoxysilylpropionic ester having the general formula (6), and
partial hydrolyzates thereof,
(R.sup.2O).sub.3SiOC(OR.sup.3)CHCH.sub.3 (5)
(R.sup.2O).sub.3SiCH(CH.sub.3)COOR.sup.3 (6)
wherein R.sup.2 and R.sup.3 are as defined above.
[0019] The second part comprises
[0020] (F) 150 to 10 parts by weight of an organopolysiloxane
having the general formula (7):
HO(SiR.sup.1.sub.2O).sub.nH (7)
wherein R.sup.1 and n are as defined above,
[0021] (G) 0.01 to 10 parts by weight of an organotin catalyst,
and
[0022] (H) 0.1 to 10 parts by weight of water. It is assumed that
the total amount of components (A) and (F) is 200 parts by weight,
and the amounts of components (B) to (E) in the first part and the
amounts of components (G) and (H) in the second part are relative
to the total amount of components (A) and (F) which is 200 parts by
weight.
[0023] In a preferred embodiment, component (A) is 80 to 120 parts
by weight and component (F) is 120 to 80 parts by weight, with the
proviso that the total amount of components (A) and (F) is 200
parts by weight.
[0024] The composition is typically used as a sealant in automotive
parts or electrical and electronic parts.
ADVANTAGEOUS EFFECTS OF INVENTION
[0025] The two-part organopolysiloxane composition effectively
cures even under low temperature and low humidity conditions under
which prior art room temperature curable organopolysiloxane
compositions are not curable. A satisfactory rubbery elastomer is
briefly produced. The composition is advantageously used as
adhesives and sealants, especially as sealants in the automotive
and electrical and electronic applications.
DESCRIPTION OF EMBODIMENTS
[0026] The two-part organopolysiloxane composition of the invention
is defined as comprising a first part comprising components (A) to
(E) and a second part comprising components (F) to (H). After the
first and second parts are mixed together, the resulting
composition cures briefly.
[0027] Component (A) in the first part is an organopolysiloxane
having the general formula (1).
HO(SiR.sup.1.sub.2O).sub.nH (1)
[0028] In formula (1), R.sup.1 is each independently a substituted
or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon
atoms, examples of which include alkyl groups such as methyl,
ethyl, propyl, butyl, hexyl and octyl, cycloalkyl groups such as
cyclohexyl, alkenyl groups such as vinyl, allyl, propenyl, butenyl,
and hexenyl, aryl groups such as phenyl and tolyl, aralkyl groups
such as benzyl and phenylethyl, and substituted forms of the
foregoing in which some or all hydrogen atoms are replaced by
halogen atoms (e.g., chloro, fluoro or bromo), such as
trifluoropropyl. Inter alia, methyl and phenyl are preferred, with
methyl being most preferred. Groups R.sup.1 may be the same or
different.
[0029] In formula (1), n is an integer of at least 10, and
preferably such an integer that the organopolysiloxane may have a
viscosity in the range of 25 to 500,000 mPa-s, more preferably 500
to 100,000 mPa-s at 25.degree. C. Note that the viscosity is
measured at 25.degree. C. by a rotational viscometer.
[0030] In the composition of the invention, the total amount of
components (A) and (F) is 200 parts by weight. The amount of
component (A) in the first part is 50 to 190 parts by weight (to be
combined with 150 to 10 parts by weight of component (F)),
preferably 70 to 150 parts by weight (to be combined with 130 to 50
parts by weight of component (F)), more preferably 80 to 120 parts
by weight (to be combined with 120 to 80 parts by weight of
component (F)), and even more preferably 90 to 110 parts by weight
(to be combined with 110 to 90 parts by weight of component (F)).
If the amount of component (A) is less than 50 pbw (to be combined
with more than 150 pbw of component (F)) or more than 190 pbw (to
be combined with less than 10 pbw of component (F)), then the
fast-cure behavior may be unsatisfactory. Note that "part by
weight" is sometimes abbreviated as "pbw."
[0031] Component (B) is a ketene silyl acetal compound having the
general formula (2), a 2-methyldialkoxysilylpropionic ester having
the general formula (3), or a partial hydrolyzate thereof. It is
essential for alkoxylating component (A) at both ends.
(R.sup.2O).sub.2Si(R.sup.3)OC(OR.sup.3)CHCH.sub.3 (2)
(R.sup.2O).sub.2Si(CH.sub.3)CH(CH.sub.3)COOR.sup.3 (3)
Herein R.sup.2 is an alkyl group of 1 to 4 carbon atoms, R.sup.3 is
a substituted or unsubstituted alkyl group of 1 to 12 carbon atoms,
R.sup.2 and R.sup.3 may be the same or different,
[0032] In formulae (2) and (3), R.sup.2 is an alkyl group of 1 to 4
carbon atoms, which may be either straight or branched. Examples
include methyl, ethyl, propyl, n-butyl, isopropyl, tert-butyl,
sec-butyl, and isobutyl. Groups R.sup.2 may be the same or
different.
[0033] R.sup.3 is an alkyl group of 1 to 12 carbon atoms, which may
be straight, cyclic or branched. Examples include straight alkyl
groups such as methyl, ethyl, propyl, n-butyl, hexyl, heptyl,
octyl, nonyl and decyl, cyclic alkyl groups such as cyclohexyl,
branched alkyl groups such as tert-butyl and 2-ethylhexyl, and
halo-substituted forms of the foregoing in which some or all
hydrogen atoms are replaced by halogen atoms (e.g., chloro, fluoro
or bromo), such as chloromethyl, bromoethyl and trifluoropropyl.
Groups R.sup.3 may be the same or different.
[0034] Preferably R.sup.2 is methyl or ethyl, with methyl being
more preferred. Also preferably R.sup.3 is methyl, ethyl, n-butyl,
or 2-ethylhexyl, with 2-ethylhexyl being more preferred. Component
(B) used herein may be a single compound or a mixture of two or
more compounds.
[0035] Since the ketene silyl acetal compound of formula (2) and
the 2-methyldialkoxysilylpropionic ester of formula (3) are
isomers, they are available as a mixture from hydrosilylation
reaction between an acrylic ester and a methyldialkoxysilane. A
commercially available compound may be used such as OCMS-2
(Shin-Etsu Chemical Co., Ltd.).
[0036] The ketene silyl acetal compound,
2-methyldialkoxysilylpropionic ester or partial hydrolyzate thereof
as component (B) is used in an amount of 0.1 to 20 parts by weight,
preferably 1 to 15 parts by weight relative to 200 parts by weight
of components (A) and (F) combined. Outside the range, less amounts
of component (B) may be insufficient to alkoxylate component (A) at
both ends with component (B), resulting in a composition which is
poor in storage stability and appearance or builds up its
viscosity. Excessive amounts of component (B) may lead to an
extended curing time and rubber with poor mechanical properties,
and be costly.
[0037] Component (C) is an organic compound and/or silane compound
having at least one nitrogen atom in the molecule. It is an
essential catalyst for facilitating efficient terminal modification
of component (A) with component (B) within a short time.
[0038] Typical of the organic compound having at least one nitrogen
atom in the molecule are amine compounds including primary amines
such as methylamine, ethylamine, propylamine, butylamine, and
octylamine, secondary amines such as dimethylamine, dipropylamine,
dibutylamine, and dioctylamine, and tertiary amines such as
trimethylamine, triethylamine, tripropylamine, tributylamine, and
trioctylamine. Typical of the silane compound having at least one
nitrogen atom in the molecule are alkoxysilanes including
3-aminopropyldiethoxymethylsilane, 3-aminopropyltriethoxysilane,
3-aminopropyldimethoxymethylsilane, 3-aminopropyltrimethoxysilane,
3-aminomethyltriethoxysilane, 3-aminomethyltrimethoxysilane,
3-(2-aminoethylaminopropyl)dimethoxymethylsilane,
3-(2-aminoethylaminopropyl)trimethoxysilane,
2-aminoethylaminomethyldimethoxymethylsilane,
2-aminoethylaminomethyltrimethoxysilane, and
1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine. The
organic compound or silane compound having at least one nitrogen
atom in the molecule is not particularly limited as long as it
displays basicity in air. Inter alia, 3-aminopropyltriethoxysilane
and 1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine are
preferred, with the latter being more preferred.
[0039] The organic compound or silane compound having at least one
nitrogen atom in the molecule as component (C) is used in an amount
of 0.01 to 20 parts by weight, preferably 0.1 to 10 parts by weight
relative to 200 parts by weight of components (A) and (F) combined.
Outside the range, less amounts of component (C) may be
insufficient to alkoxylate component (A) at both ends with
component (B). Excessive amounts of component (C) may adversely
affect odor and shelf stability.
[0040] Component (D) is a silane compound having at least two,
preferably at least three alkoxy groups in the molecule or a
partial hydrolytic condensate thereof which helps the composition
cure more appropriately. This silane compound has the general
formula (4):
R.sup.5.sub.mSi(OR.sup.4).sub.4-m (4)
wherein R.sup.4 is an unsubstituted or alkoxy-substituted
monovalent hydrocarbon group of 1 to 4 carbon atoms, R.sup.5 is a
substituted or unsubstituted monovalent hydrocarbon group of 1 to
10 carbon atoms, and m is 0, 1 or 2.
[0041] In formula (4), R.sup.4 is an optionally alkoxy-substituted
monovalent hydrocarbon group of 1 to 4 carbon atoms. Suitable
monovalent hydrocarbon groups include alkyl groups of 1 to 4 carbon
atoms such as methyl, ethyl, propyl and butyl. Suitable
alkoxy-substituted alkyl groups include methoxymethyl,
ethoxymethyl, propoxymethyl, butoxymethyl, pentyloxymethyl,
methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl,
methoxypropyl, ethoxypropyl, propoxypropyl, methoxybutyl,
ethoxybutyl, and methoxypentyl. Inter alia, methyl and ethyl are
preferred.
[0042] R.sup.5 is an optionally substituted monovalent hydrocarbon
group of 1 to 10 carbon atoms, examples of which include alkyl
groups such as methyl, ethyl, propyl, butyl, hexyl and octyl,
cycloalkyl groups such as cyclohexyl, alkenyl groups such as vinyl,
allyl, propenyl, butenyl, and hexenyl, aryl groups such as phenyl
and tolyl, aralkyl groups such as benzyl and phenylethyl, and
substituted forms of the foregoing in which some or all hydrogen
atoms are replaced by halogen atoms (e.g., chloro, fluoro or
bromo), such as trifluoropropyl. Inter alia, methyl and phenyl are
preferred, with methyl being most preferred. Groups R.sup.5 may be
the same or different.
[0043] Illustrative examples of the silane compound include
alkoxysilanes such as tetramethoxysilane, ethyl silicate, propyl
silicate, methyltrimethoxysilane, methyltriethoxysilane,
vinyltrimethoxysilane, vinyltriethoxysilane,
phenyltrimethoxysilane, phenyltriethoxysilane,
methyltris(methoxyethoxy)silane, vinyltris(methoxyethoxy)silane,
dimethyldimethoxysilane, dimethyldiethoxysilane,
diphenyldimethoxysilane, and vinylmethyldimethoxysilane, and
partial hydrolytic condensates thereof. The partial hydrolytic
condensates may be straight, branched or cyclic. The partial
hydrolytic condensates are generally oligomers having a degree of
polymerization of about 2 to 8. Component (D) used herein may be a
single compound or a mixture of two or more compounds.
[0044] The silane compound having at least two alkoxy groups in the
molecule or partial hydrolytic condensate thereof as component (D)
is used in an amount of 0.1 to 30 parts by weight, preferably 1 to
15 parts by weight relative to 200 parts by weight of components
(A) and (F) combined. Outside the range, less amounts of component
(D) may allow for an extremely fast cure rate which is unfavorable
in working. Excessive amounts of component (D) may adversely affect
mechanical properties of rubber.
[0045] Component (E) is a ketene silyl acetal compound having the
general formula (5), a 2-trialkoxysilylpropionic ester having the
general formula (6), or a partial hydrolyzate thereof. It is an
essential component capable of reacting with the silanol-containing
organopolysiloxane in the second part to provide a satisfactory
fast-cure behavior.
(R.sup.2O).sub.3SiOC(OR.sup.3)CHCH.sub.3 (5)
(R.sup.2O).sub.3SiCH(CH.sub.3)COOR.sup.3 (6)
Herein R.sup.2 and R.sup.3 are as defined above.
[0046] In formulae (5) and (6), exemplary groups of R.sup.2 and
R.sup.3 may be the same as R.sup.2 and R.sup.3 in formulae (2) and
(3). The groups of R.sup.2 and R.sup.3 may be the same or
different. Preferably R.sup.2 is methyl or ethyl, with methyl being
more preferred. Also preferably R.sup.3 is methyl, ethyl, n-butyl,
or 2-ethylhexyl, with ethyl being more preferred. Component (E)
used herein may be a single compound or a mixture of two or more
compounds.
[0047] Since the ketene silyl acetal compound of formula (5) and
the 2-trialkoxysilylpropionic ester of formula (6) are isomers,
they are available as a mixture from hydrosilylation reaction
between an acrylic ester and a trialkoxysilane. A commercially
available compound may be used such as ECMS (Shin-Etsu Chemical
Co., Ltd.).
[0048] The ketene silyl acetal compound, 2-trialkoxysilylpropionic
ester or partial hydrolyzate thereof as component (E) is preferably
added after components (A) and (B) are mixed, more preferably after
at least 5 minutes from mixing of components (A) and (B). If
component (E) is added before silanol groups in component (A) are
modified with alkoxy groups in component (B), then the resulting
composition is sometimes unstable in air. The order of addition of
components (C) and (D) is not particularly limited.
[0049] The ketene silyl acetal compound, 2-trialkoxysilylpropionic
ester or partial hydrolyzate thereof as component (E) is used in an
amount of 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by
weight relative to 200 parts by weight of components (A) and (F)
combined. Outside the range, less amounts of component (E) may fail
in fast-cure behavior. Excessive amounts of component (E) may lead
to an extremely fast cure rate which is unfavorable in working,
adversely affect mechanical properties of rubber, and be
costly.
[0050] Reference is now made to the second part. Component (F) is
an organopolysiloxane having the general formula (7):
HO(SiR.sup.1.sub.2O).sub.nH (7)
wherein R.sup.1 and n are as defined above for formula (1).
[0051] In formula (7), R.sup.1 is each independently a substituted
or unsubstituted monovalent hydrocarbon group of 1 to 10 carbon
atoms, examples of which include alkyl groups such as methyl,
ethyl, propyl, butyl, hexyl and octyl, cycloalkyl groups such as
cyclohexyl, alkenyl groups such as vinyl, allyl, propenyl, butenyl,
and hexenyl, aryl groups such as phenyl and tolyl, aralkyl groups
such as benzyl and phenylethyl, and substituted forms of the
foregoing in which some or all hydrogen atoms are replaced by
halogen atoms (e.g., chloro, fluoro or bromo), such as
trifluoropropyl. Inter alia, methyl and phenyl are preferred, with
methyl being most preferred. Groups R.sup.1 may be the same or
different.
[0052] In formula (7), n is an integer of at least 10, and
preferably such an integer that the organopolysiloxane may have a
viscosity in the range of 25 to 500,000 mPa-s, more preferably 500
to 100,000 mPa-s.
[0053] Although component (F) may have a different substituent or
degree of polymerization from component (A), component (F) is
preferably the same as component (A). The amount of component (F)
compounded is as described above.
[0054] Component (G) is an organotin catalyst which is essential
for the composition to cure. Examples of the organotin catalyst
include organotin compounds such as dimethyldimethoxytin,
dibutyltin diacetate, dibutyltin dioctoate, dibutyltin
dibenzylmaleate, dioctyltin diacetate, and dioctyltin diversatate.
These compounds may be used alone or in admixture of two or
more.
[0055] Component (G) is used in an amount of 0.01 to 10 parts by
weight, preferably 0.05 to 1 part by weight relative to 200 parts
by weight of components (A) and (F) combined. With less than 0.01
pbw of component (G), surface cure may be retarded. More than 10
pbw of component (G) may lead to an extremely fast cure rate to
interfere with the working process, form a composition which lacks
elongation, and adversely affect mechanical properties of
rubber.
[0056] Component (H) is water which is essential for rendering the
composition fast curable. Water is used in an amount of 0.1 to 10
parts by weight, preferably 0.5 to 4 parts by weight relative to
200 parts by weight of components (A) and (F) combined. The
composition may cure slowly in the presence of less than 0.1 pbw of
water whereas more than 10 pbw of water may be detrimental to
curing.
[0057] The second part may be prepared by mixing components (F) to
(H) in a standard way.
[0058] To the two-part organopolysiloxane composition comprising
components (A) to (H) mentioned above, at least one filler is
preferably added if necessary for improving flow properties prior
to curing and imparting desired mechanical properties to the cured
rubbery elastomer. The filler may be added to the first and/or
second part. Examples of suitable fillers include silica such as
fumed silica and wet silica, which are optionally treated with
organosilicon compounds (e.g., silanes, silazanes and siloxanes),
carbon powder, talc, bentonite, calcium carbonate, zinc carbonate,
and magnesium carbonate which are optionally surface treated with
fatty acids or resin acids, calcium oxide, zinc oxide, magnesium
oxide, aluminum oxide and aluminum hydroxide, which are optionally
surface treated. Surface treated fillers having a minimal content
of water are preferred. The filler is preferably used in an amount
of 2 to 600 parts by weight relative to 200 parts by weight of
components (A) and (F) combined.
[0059] The two-part organopolysiloxane composition is obtained by
combining components (A) to (E) to form the first part, combining
components (F) to (H) to form the second part, and adding any
desired additives to either one or both of these parts in a
humidity-shielded state, if desired. The first and second parts are
contained and held in separate sealed containers until use when
they are mixed together and cured into a rubbery elastomer. Use is
in the standard way of so-called two-part organopolysiloxane
compositions.
[0060] After two parts are combined, the two-part
organopolysiloxane composition cures with water in the second part
and airborne moisture and at the same time, component (E) reacts
with component (F) in air in the presence of component (C), whereby
cure occurs not only from the surface, but also from the interior
of the composition. That is, fast cure and deep-section cure take
place at the same time. The cure rate can be controlled by changing
the viscosity of component (A) as a base polymer and the amount of
component (E) added. Since the cured composition has improved
mechanical properties, a sealant having excellent properties is
provided.
[0061] The composition is useful as sealants and adhesives,
particularly in the automotive and electrical and electronic
applications.
[0062] It is noted that the curing conditions for the two-part
organopolysiloxane composition are not particularly limited.
Advantageously, the two-part organopolysiloxane composition may
cure under low temperature and low humidity conditions which are
not acceptable to prior art room temperature-curable
organopolysiloxane compositions.
EXAMPLE
[0063] Examples and Comparative Examples are given below by way of
illustration and not by way of limitation.
Example 1
[0064] To 100 parts by weight of a silanol end-capped
polydimethylsiloxane having a viscosity of 5,000 mPa-s at
25.degree. C. were added 5 parts by weight of the reaction product
of 2-ethylhexyl acrylate with dimethoxymethylsilane (trade name
OCMS-2, Shin-Etsu Chemical Co., Ltd.) and 0.6 part by weight of
1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine. The
ingredients were mixed on a mixer to effect reaction. To the
reaction mixture were added 10 parts by weight of a partial
hydrolytic condensate of methyltrimethoxysilane (trade name KC-89E,
Shin-Etsu Chemical Co., Ltd.), 5 parts by weight of
3-aminopropyltriethoxysilane, and 1 part by weight of the reaction
product of ethyl acrylate with trimethoxymethylsilane (trade name
ECMS, Shin-Etsu Chemical Co., Ltd.). The ingredients were
thoroughly mixed under vacuum, yielding a first part.
[0065] To 100 parts by weight of a silanol end-capped
polydimethylsiloxane having a viscosity of 5,000 mPa-s at
25.degree. C. were added 1 part by weight of water and 0.2 part by
weight of dioctyltin diversatate. The ingredients were mixed on a
mixer, yielding a second part.
[0066] The first and second parts were mixed in a volume ratio of
about 1:1, yielding sample #1.
Example 2
[0067] To 100 parts by weight of a silanol end-capped
polydimethylsiloxane having a viscosity of 5,000 mPa-s at
25.degree. C. were added 5 parts by weight of the reaction product
of 2-ethylhexyl acrylate with dimethoxymethylsilane (trade name
OCMS-2, Shin-Etsu Chemical Co., Ltd.) and 0.6 part by weight of
1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine. The
ingredients were mixed on a mixer to effect reaction. To the
reaction mixture were added 10 parts by weight of a partial
hydrolytic condensate of methyltrimethoxysilane (trade name KC-89E,
Shin-Etsu Chemical Co., Ltd.), 5 parts by weight of
3-aminopropyltriethoxysilane, and 3 parts by weight of the reaction
product of ethyl acrylate with trimethoxymethylsilane (trade name
ECMS, Shin-Etsu Chemical Co., Ltd.). The ingredients were
thoroughly mixed under vacuum, yielding a first part.
[0068] To 100 parts by weight of a silanol end-capped
polydimethylsiloxane having a viscosity of 5,000 mPa-s at
25.degree. C. were added 1 part by weight of water and 0.2 part by
weight of dioctyltin diversatate. The ingredients were mixed on a
mixer, yielding a second part.
[0069] The first and second parts were mixed in a volume ratio of
about 1:1, yielding sample #2.
Comparative Example 1
[0070] A composition, designated sample #3, was prepared under the
same conditions as in Example 1 except that the reaction product of
ethyl acrylate with trimethoxymethylsilane was omitted from the
first part.
Comparative Example 2
[0071] A composition, designated sample #4, was prepared under the
same conditions as in Example 1 except that water was omitted from
the second part.
Comparative Example 3
[0072] A composition, designated sample #5, was prepared under the
same conditions as in Example 1 except that
1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine and
3-aminopropyltriethoxysilane (component (C)) were omitted from the
first part.
Comparative Example 4
[0073] A composition, designated sample #6, was prepared under the
same conditions as in Example 1 except that dioctyltin diversatate
was omitted from the second part.
[0074] The samples obtained in Examples and Comparative Examples
were examined by the following tests.
Tests
[0075] The desired sample of the two-part organopolysiloxane
composition of each of Examples and Comparative Examples was
obtained by charging a sealed container with first and second parts
in a volume ratio of about 1:1 and mixing together. The composition
(sample) thus mixed was cast into a mold of 2 mm deep and cured at
23.degree. C. and RH 50% for 3 days, obtaining a rubber sheet of 2
mm thick. The rubber conversion time was determined as a time taken
until the composition mixed as above cured under the sealed
conditions into rubber. A tack-free time was measured by the method
according to JIS A5758. Rubber physical properties of the 2-mm
thick sheet were measured according to JIS K6249.
[0076] In Examples and Comparative Examples, the first and second
parts were separately shelf stored at room temperature for 6 months
before the same tests were carried out.
[0077] The test results of Examples 1 and 2 and Comparative
Examples 1 to 4 are shown in Table 1.
TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 1 2 3 4
Initial Rubber conversion time, min 15 5 >120 >120 >120
>120 Physical Tack-free time, min 5 3 60 120 >120 >120
properties Hardness, Durometer A 22 24 24 2 uncured uncured
Elongation at break, % 90 120 150 300 Tensile strength, MPa 0.4 0.5
0.3 0.1 After Rubber conversion time, min 20 10 >120 >120
>120 >120 RT/6 month Tack-free time, min 6 5 60 120 >120
>120 storage Hardness, Durometer A 24 23 22 2 uncured uncured
Elongation at break, % 80 80 180 310 Tensile strength, MPa 0.3 0.3
0.3 0.1
[0078] Japanese Patent Application No. 2009-185585 is incorporated
herein by reference.
[0079] Although some preferred embodiments have been described,
many modifications and variations may be made thereto in light of
the above teachings. It is therefore to be understood that the
invention may be practiced otherwise than as specifically described
without departing from the scope of the appended claims.
* * * * *